1. Field of the Invention.
The invention falls within the realms of electronic engineering specifically of semiconductor devices, namely, light-emitting diodes, and finds its application in semiconductor engineering in the development and manufacture of light-emitting diodes used in power, railway and automobile transport, ferrous metallurgy, chemical, heavy and other industries.
2. Description of the Prior Art.
Light-emitting diodes are widely used in signaling information as to modes of operation of various devices for the illumination of screens, in the manufacture of information sources such as information panels, traffic lights, traveling lines, additional signals of braking in automobiles, etc. See German Patent No. 20 62 209, issued Jan. 9, 1975; German Patent No. 35 32 821 issued Dec. 12, 1992; U.S. Pat. No. 4,907,044 issued Mar. 6, 1990; International PCT Patent Application No. PCT/US94/10781 filed Apr. 6, 1995; and Svetodiody [Light-Emitting Diodes], by A. Berg and P. Din (1979).
The use of light-emitting diodes instead of incandescent lamps considerably increases reliability and reduces the power consumption by the equipment used. Because of this increase in use, there are now required in many cases light-emitting diodes that have a wide range of colors and shades of light flow, and that are of various sizes and varying uniformity as to the luminous spot and different emission powers (luminous intensities).
The most important parameter in working with light-emitting diodes is the emission power which depends mostly on the amount of forward flow of electrical current and the thermal resistance value of the holder on which a crystal of light emitter is installed.
Already known to the prior art is a light-emitting diode with a red color luminescence of HLMP-C100 type in which the crystal of the light-emitter is fixed onto a holder connected to one of the electrical outlets and located in a plastic monolithic casing. This casing consists of a hemispheric lens, 5 mm in diameter, which concentrates the emission, and a cylindrical base. See Optoelectronics Designers""s Catalog, Hewlett Packard (1993), pp. 3-44. With the forward current being equal to 20 mA, the minimum value of light intensity is 0.29 Cd at an angle of vision of xc2x1xc2x130xc2x0 at half power of emission. The value of thermal resistance of the casing is 210xc2x0 C./W. The drawback of such a light-emitting diode is its low light intensity. This low intensity is caused by the fact that it is impossible to increase the value of forward current strength via a unit because of considerable thermal resistance from the casing and overheating of the crystal of the light emitter due to the fact that the released heat is removed by means of a metallic outlet only. Here a disturbance of the linearity of the lumen-ampere characteristic is observed. This inhibits the rise of luminous intensity that accompanies the increases in the level of forward current.
Also known is a light-emitting diode having infrared radiation of the CQX 19 type, in which a crystal of a light-emitter is installed on the holder of the casing TO-39. See A Selection Guide to Optoelectronic Devices, Catalog AEG Telefunken (1982), p. 11. A hemispheric lens 8 mm in diameter is formed on this holder. When forward electrical current is equal to 250 mA, the power for releasing an emission constitutes 20 mW with an angle of vision of xe2x88x92xc2x1xc2x120xc2x0 at half power of emission. The value of the thermal resistance is equal to 250 to 300xc2x0 C./W, which is a considerable value and does not permit the emission power to be raised by increasing the level of the forward current.
An effective red color light-emitting diode of the I N 6092 type is the most suitable for the light-emitting diode, according to its technical principle. See S. M. Zee, Fizika poluprovodnikovykh priborov (vol. 2, 2d ed., M. Mir: 1984, p. 289, FIG. 16a. This light-emitting diode, taken as a prototype, contains a metallic glass holder with electrical outlets, a crystal of a light-emitter with ohmic contacts that are installed on the holder by means of a current-transmitting glue and connected through the conductor with the appropriate outlet, and also a metallic cover with a lens that concentrates the emission produced by the crystal.
The allowable forward electrical current through this device is 35 mA, the thermal resistance is xe2x88x92425xc2x0 C./W, the angle of vision is xc2x1xc2x118xc2x0 at half emission power, while the standard value of emission power is 5 mcd when the forward current is 20 mA.
It is obvious that the drawback of this light-emitting diode is its low emission power and the high value of thermal resistance that is caused by the weak dissipation of heat produced by the crystal of light-emitter only through the outlet on which this crystal is installed. This limitation of the dissipation power value does not permit the flow of high forward current due to a disturbance of the linearity of the lumen-ampere characteristic of the light-emitting diode.
The set task and aim of this invention is to increase the emission power of the diode, thus making it possible to vary the angle of vision of the device.
The invention also has as its goals increased accuracy of the coaxal hemispheric lens and the crystal of the light emitter, and an increased ability to work with light-emitting diodes at an ambient temperature of less than 60xc2x0 C.
The set task is solved through the development of a light-emitting diode in accordance with the invention in which a cover with a hemispheric lens on a cylindrical base having a thickness (the height of the cylinder) not exceeding the size of the hemispheric lens radius. Pins are disposed on the lower face of the cylindrical base. These pins are located in accordance with the positions of the holes in a holder-substrate. The holder-substrate has a thickness equal to or exceeding four thicknesses of the crystal of the light emitter. See X. The holder-substrate contains a mounting seat for a crystal of the light-emitter in the form of a recess with a flat bottom and a lateral surface in the form of a body of revolution, chiefly truncated conical surface, reflecting the emissions. It also has a flat bottom on which the crystal of light emitter is installedxe2x80x94with the flat mounting seat crystal of the light-emitter in recess. Here, the depth of the mounting seat of the crystal of the light-emitter exceeds two thicknesses of the indicated crystal of the light-emitter, whereas the diameter of the flat mounting seat in the recess exceeds the size of the diameter of the lower face of the crystal of the light-emitter, but is less than one and a half the values of this size. In addition, the space between the lower face of the cylindrical base and the upper surface of the holder-substrate in the light-emitting diode is filled with polymeric sealing compound. At the junction of the conductor and the isolated connecting outlet, a layer of current-transmitting glue is applied.